Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Amortized Cost, Due in one year or less	$ 9,132
Amortized Cost, Due after one year through five years	31,533
Amortized Cost, Due after five years through ten years	45,283
Amortized Cost, Due after ten years	207,478
Amortized Cost, Mortgage-backed securities	184,553
Amortized Cost, Total securities available for sale	477,979	$ 336,316
Fair Value, Due in one year or less	9,172
Fair Value, Due after one year through five years	31,732
Fair Value, Due after five years through ten years	47,236
Fair Value, Due after ten years	221,852
Fair Value, Mortgage-backed securities	188,157
Fair Value, Total securities available for sale	$ 498,149	$ 363,464

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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